Method for gluing plastic objects with a hot-melt adhesive

ABSTRACT

In a method for bonding plastic objects together by means of a hot-melt type of adhesive, in addition to or during the heating and addition of a plasticizer-resistant hot-melt adhesive, at least one of the objects to be bonded, is heated up in the area to be bonded beyond the melting temperature of the material of which it is made. The method is particularly advantageous for the joining together of multi-layered plastic pipes. The result is the generation of a method for bonding objects by means of a hot-melt type of adhesive that can also be applied with materials for which it was hitherto impossible to apply hot-melt adhesion.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a method for bonding plastic objects togetherusing a hot-melt type of adhesive.

Objects made of all kinds of different materials are attached togetherby applying adhesives used in the shape of sticks, powders or slabs. Allsorts of plastic materials, such as polyamides and polypropylenes, areused as the basis for these hot-melt adhesives. The objects are usuallybonded together by applying the hot-melt adhesive in a heated, in otherwords free-flowing, condition to at least one of the surfaces to bebonded, which is at room temperature, after which the two surfaces to bebonded are pressed against each other. After a short cooling-off period,the two objects are then securely bonded together.

2. Description of Related Art

The process is already known whereby the hot-melt adhesive is firstapplied to the object, the hot-melt adhesive is then heated above itsmelting temperature and the two objects are then pressed together. Thishas been proposed for example for the bonding of floor coverings, inwhich the hot-melt adhesive is heated up through the floor covering. Thefloor covering itself was not heated up above its own respective meltingtemperature, however.

According to a further proposal, installation cases are bonded to themasonry by the process of first heating up the masonry and thenattaching the cases by means of a hot-melt adhesive. Also in this case,the masonry's own melting temperature is not exceeded.

And yet all these methods are unsuitable for some materials, or theultimate solidity achieved is not sufficient.

BRIEF SUMMARY OF THE INVENTION

The aim of the invention is to establish a method for bonding objectstogether using a hot-melt type of adhesive that can also be used withmaterials with which it was hitherto impossible to make use of hot-meltadhesion. This has been achieved by means of heating at least one of theobjects to be bonded, in particular multi-layered pipes, in the area inwhich it is to be bonded to a temperature higher than the meltingtemperature of the material of which the object is made, in addition toor at the same time as heating and adding a plasticizer-resistanthot-melt type of adhesive.

DETAILED DESCRIPTION OF THE INVENTION

As experiments carried out have demonstrated, when the method accordingto the invention is applied, the components of the materials of theobjects to be bonded on the one hand and the hot-melt adhesive on theother hand mix together in such a way that an homogeneous and thus alsosolid bond results. Any plasticizers that may be present, which wouldotherwise disturb the ability to bond, have no disadvantageous effectwhen the method according to the invention is applied. Even suchmaterials as polyethylene (PE) can be bonded together using the methodaccording to the invention.

Within the framework of the invention, it is possible to heat up atfirst at least one of the objects to be attached, in the area where itis to be bonded, until its temperature exceeds the melting temperatureof the materials of which the object is made, and subsequently tointroduce the hot-melt adhesive.

When materials are bonded that have such different melting points thatthere is a risk that when the higher melting point is reached, thematerial with the lower melting point could be destroyed, it is possiblefirst to heat the one object in the area to be bonded so that itsmelting temperature is exceeded and then to mix it with the hot-meltadhesive flowing in, after which, in a second phase, the hot-meltadhesive that has already been cooled down after being mixed with thematerial of the first object is re-heated and bonded with the materialof the second object.

It is also possible to execute the method according to the invention,however, in such a way that the hot-melt adhesive is heated up to such atemperature and for such a long time that the materials to be bondedmelt and flow into the hot-melt adhesive.

There now follows a description of the invention in greater detail, withthe aid of the embodiment illustrated in the drawing, although withoutthe application of the method according to the invention beingrestricted to this embodiment.

BRIEF DESCRIPTION OF THE DRAWING

The drawing illustrates a section cut part of the way through a point atwhich two pipes are bonded.

In accordance with the drawing, two pipes 1 and 2 are connectedtogether. These pipes is 1 and 2 have a multi-layered construction andare fitted, for the purpose of mechanical reinforcement, withscrew-shaped components 3 stretching along their length and made of hardPVC. Between these “screws” 3 made of hard PVC are other components 4made of soft PVC, which enable the pipes 1 and 2 to be deformed. Insidetheir structures, the pipes 1 and 2 contain an inner pipe 5 made ofpolyurethane.

The terminal areas 6 of the two pipes 1 and 2 are heated up above themelting temperatures at least of the components 3 and 4 and a hot-meltadhesive is introduced. In the area 6, the materials thus melted havemixed to such an extent that an homogeneous bond has taken place betweenpipes 1 and 2.

What is claimed is:
 1. A method for bonding plastic objects together bymeans of a hot-melt adhesive, comprising in addition to or together withthe heating and application of a plasticizer-resistant hot-meltadhesive, heating up a first object to be bonded in the area to bebonded above the melting temperature of the materials of which theobject is made, subsequently applying the hot melt adhesive to theheated area of the first object, wherein the hot melt adhesive flowsinto and mixes with the heated area of the first object, and thenbonding the first object with a second object.
 2. The method of claim 1wherein the first object is heated up in the area to be bonded beyondthe melting temperature of the material of which it is made and thenmixed with the hot-melt adhesive flowing in, after which in a secondphase the hot-melt adhesive that has already been cooled down aftermixing with the material of the first object is reheated and bonded withthe material of the second object.
 3. The method according to claim 1wherein the hot-melt adhesive is heated up to such a temperature and forsuch a long time that the materials to be bonded melt and flow into thehot-melt adhesive.
 4. The method according to claim 1 wherein theobjects to be bonded comprise multi-layered pipe.